As air travel has increased over the past decades, airport facilities have become more crowded and congested. Minimizing the time between the arrival of an aircraft and its departure to maintain an airline's flight schedule, and also to make a gate or parking location available without delay to an incoming aircraft, has become an airline priority. The safe and efficient ground movement of a large number of aircraft simultaneously into and out of the ramp and gate areas has become increasingly important. As airline fuel costs and safety concerns and regulations have increased, use of the aircraft main engines is no longer the best option for achieving the desired safe and efficient ground movement.
Various alternatives to the use of an aircraft's main engines to move an aircraft on the ground have been tried. The use of a tug or tow vehicle to move an aircraft into and out of a gate or parking location can eliminate the need to use the aircraft main engines. This option, however, is not without its own challenges and costs. More ground vehicles, requiring more fuel and more ground personnel to operate them, add to an already congested environment in the gate area. Restricted use of the aircraft engines on low power during arrival at or departure from a gate is an additional option. This option is also problematic, however. Not only does engine use consume fuel, it is also noisy, and the associated safety hazards of jet blast and engine ingestion in a congested area are significant concerns that cannot be overlooked.
The use of a motor structure integrally mounted with a wheel to rotate the wheel and drive a vehicle, including an aircraft, has been proposed. The use of such a structure, ideally, could move an aircraft with minimal or no use of an aircraft's main engines. In U.S. Pat. No. 2,430,163, for example, Dever describes a motor that may be incorporated in an aircraft landing gear wheel in which the stator is mounted on a stationary part of a wheel assembly and the rotor is connected to the revolving part of the wheel to produce a high rotating torque near the periphery of the wheel. The structure described by Dever includes disc type wheels with webs that are dished to form a conical space near the hub to accommodate the motor. Dever does not suggest a wheel configuration that maximizes this space. Moreover, Dever does not mention including a gear assembly integrated with the wheel structure described therein.
Other patent art, such as U.S. Pat. No. 3,977,631 to Jenny, also describes drive motors associated with aircraft gear wheels intended to drive an aircraft on the ground. The motor assembly disclosed by Jenny is selectively coupled to an aircraft wheel through a rotatably mounted brake apparatus in which the normally non-rotating stator is rotatably mounted and driven. A reduction gear assembly is included in this arrangement and is positioned to facilitate mounting of a drive motor away from the cramped wheel and brake assembly. The configuration of the wheel itself is not mentioned.
In U.S. Pat. No. 7,445,178, McCoskey et al describe a powered nose aircraft wheel system with a multifunctional wheel motor coupled to the wheel axle and the wheel. The motor, which may be driven by a planetary gear assembly or by a direct drive, is located within the hub of the wheel, and the wheels are free to spin on an axle strut by rim bearings. The stator winding is rigidly fixed to the axle and partially contained by a rotor, which rotates on bearings about the axle. The wheel shape shown by McCoskey et al does not integrate the motor within the wheel, nor is it suggested that wheel supports could be located to maximize the space available for integrating the motor and gearing within the wheel. U.S. Pat. No. 7,226,018 to Sullivan also describes a wheel motor useful in an aircraft landing gear wheel. This wheel hub motor/generator disks stack includes within the stack alternating rotor and stator disks, in which the rotors are coupled to the wheel, and is designed to provide motive force to an aircraft wheel when electric power is applied. Sullivan is silent, however, with respect to both the specific shape of the wheel structure and the integration of a motor and gearing within a wheel structure. None of the foregoing patents suggests a wheel structure that is configured to maximize the limited landing gear space available to integrate within the wheel a compact motor and gear assembly capable of powering an aircraft drive wheel that could be easily installed on an existing aircraft without the modification of other landing gear structures. This art, moreover, does not contemplate a wheel structure shaped to support an integral configuration of the motor and gear components that can be retrofitted in existing aircraft or that provides easy access to the motor components for maintenance and repair when the motor is not in operation.
U.S. Pat. No. 7,469,858 to Edelson, owned in common with the present invention, describes a geared wheel motor design that may be used to move an aircraft from a stationary position for taxiing. Configuring the wheel shape to maximize the volume in which a drive motor and gear assembly may be mounted is not suggested, however.
Published United States patent applications, including U.S. Patent Application Publication Nos. US2006/0273686 to Edelson, US2007/0282491 to Cox et al, US2009/0152055 to Cox, US2009/0261197 to Cox, International Patent Application Publication No. WO 2008/027458 to Cox et al, and British Patent No. 2457144, also owned in common with the present invention, describe aircraft drive systems that use electric drive motors to power aircraft wheels and move an aircraft on the ground. These disclosures focus on specific aspects of the drive systems and motor assemblies, including drive system data, motor design, tire profile, and motor cooling, rather than on a wheel structure specifically configured to maximize space within the wheel well to integrally support motor and gear assembly components and landing gear wheel components without changes to the aircraft landing gear.
A need exists, therefore, for a wheel structure specifically configured to maximize the space available to integrate an electric motor and gear assembly substantially completely within an aircraft wheel without changes to the existing aircraft landing gear components.